MD, rifle and shotgun are scanhit weapons. If you keep the crosshair on top of moving target you will hit it. If you use a pulse rifle, you will miss it. You need to lead the target while using pulse rifle. That gets rather difficult above your 100-150ping. Now add to this your target who lags and warps (say he has 250 ping).
You obviously haven't played gpp. Gpp has projectile lag compensation. Most 1.1 servers (not all) that have unlagged does not backtrack for projectiles.
Currently the only servers that have unlagged enabled in 1.1 that supports this feature is probably just W server. You'll need a custom cgame.qvm that allows projectilenudge as well otherwise it will just ignore it.
And, also it isn't a garanteed miss if your ping is between 100-150. In 1.1, I have 0 servers under 98 ping, 4 servers between 98 and 125, 0 servers between 125 and 300. Most australians play on american servers these days. I hardly touch the slow projectile weapons in servers other than W, but even still I can use luci and pulse with some success.
I've disabled unlagged for myself in gpp several times to experiance the lagged-luci and pulse, its somewhat the easier to use though since pulse is 1.4x faster and luci bullets are twice running speed instead of jogging pace. If you learn how to play lagged and calculate estimations for aiming ahead in realtime, you'd find that it isn't that difficult.
I find lagged more fun than unlagged because it requires more skills, but is troublesome when for example, the enemy headchomp(1.1)/pounce (gpp) spam. These days I just use it as a handicap when I'm versing really bad nubs.
Anyway since the unlagged calculation for me on overseas servers is inaccurate, often graphically my bullets on unlagged go through people which is painful to look at, to the point sometimes I simply turn off my unlagged along with projectilenudge.
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I have made a video last year about me testing my mass driver with its bullet falling to the ground and isn't hitscan.
http://www.youtube.com/watch?v=39wB1VlTHxw